Method for making net structures

ABSTRACT

A method of making a net-like structure wherein groups of strands of paired groups of strands are periodically shifted to provide different pairs of such groups. Alternately with such shifting, each paired group of strands is rotated about an axis between the groups of such pair with the strand in each such group nearest such axis being rotated 180* while the remaining strands in each such group are turned through 360*.

United States Patent Fairbanks 14 1 Aug. 22, 1972 1 METHOD FOR MAKINGNET 3,591,892 7/1971 Fairbanks ..264/ 167 STRUCTURES 3,591,894 7/1971Fairbanks ..264/l67 72 I t I More F 3,331,903 7/1967 Mine ..264/D1G. 811 Liverpool E fi R D 3,518,720 7/1970 Fairbanks ..264/D1G. 81 3,525,7858/1970 Fairbanks ..264/D1G. 81 Flledi -18,1970 3,551,236 12/1970Fairbanks ..264/D1G,8l

90574 FOREIGN PATENTS 0R APPLICATIONS Related Application Data 380,3699/1969 Switzerland ..264/D1G. 81

[63] Continuation-impart of Ser. No. 849,947, Aug.

12, 1969, Pat. No. 3,591,896. Prmwry y W99 Attorney-Thomas R. OMalley,George F. Mueller 52 us. (:1. ..264/l03, 87/12, 87/53, and Eugene y156/167, 16l/DlG. 6, 264/167, 264/D1G. 81 51 int. Cl ..D04g 1/00, DOZg1/20 ABSTRACT [58] Field of Search ..264/167, 103, DIG. 81; A method ofmakin g a net like structure wherem 161/016 156/167 87/12 53 groups ofstrands of paired groups of strands are periodically shifted to providedifferent pairs of such References Cited groups. Alternately with suchshifting, each paired UMTED STATES PATENTS group of strands is rotatedabout an axis between the groups of such pair with the strand in eachsuch group 17 l2/197l y 264/ 103 nearest such axis being rotated 180while the remain g PS 6 /g; ing strands in each such group are turnedthrough omanm 3,562,046 2/1971 Guy ..156/167 3,579,729 5/1971 Fairbanks..18/12 N 6 Claims, 4 Drawing Figures METHOD FOR MAKING NET STRUCTURESThis application is a continuation-in-part of my application Ser. No.849,947, filed Aug. 12, 1969, now US. Pat. No. 3,59l ,894.

The present invention relates to a method for making net-likestructures.

In US. Pat. No. 3,331,903 there is disclosed a method and apparatus formaking a net from plastic material by extruding a plurality of pairs ofmonofilaments of plastic material in such a manner that the filaments ineach pair are spaced from each other in a first direction and the pairsof filaments are spaced from each other a given distance in a seconddirection. The monofilarnents of each pair of filaments are revolved, atthe moment of their extrusion and before being solidified, about an axisextending between the filaments of each such pair of filaments so as totwist the filaments of each pair together and to thus integrally connectthe filaments. One of the filaments of each pair of filaments is thenmoved in a second direction a distance equal to the spacing betweenpairs of filaments while continuing the extrusion of the filmnents,after which pairs of filaments are again revolved as heretoforedescribed. By continuously repeating the above steps and setting of theextruded filaments of plastic material, a net-like structure isprovided.

in my US. Pat. application entitled METHOD FOR CONTINUOUSLY EXTRUDINGNET-LIKE STRUC- TURES, Ser. No. 825,210, filed May 16, 1969 now US. Pat.No. 3,627,863, there is disclosed a method of making net-like structuresof woven or braided monofilaments using an apparatus similar to thatdescribed in US. Pat. No. 3,331,903.

Net-like structures produced in accordance with the method described inUS. Pat. No. 3,331,903 are rather stiff and, in general, do not possessa desired bulk or esthetic appeal which would encourage their use asreplacements for conventional woven fabrics. Net-like structures formedby the method disclosed in the above'noted US. Pat. No. 3,627,863 alsolack bulk and, although such structures have unbonded interlaced strandsthe strands are free to shift relative to each other when subjected toloads, thus causing distortion of the mesh openings thereof.Accordingly, a primary object of this invention is the provision of anew or improved and more satisfactory method for making net-likestructures.

Another object of this invention is to provide a method for making anet-like structure which possesses better strength and/or bulk thanconventional net-like structures and is decorative in appearance.

Still another object is a method for making a net-like structure havingunbonded interlaced strands which are stabilized against excessiveshifting relative to each other.

A further object is the provision of a new or improved extrusion methodfor making net-like structures having multiple strands extending betweenadjacent strand junctions.

A still further object is the provision of a method for continuouslyextruding net-like structures which are fonned of strands and havejunctions at each of which strands are disposed in crossing relationshipwith each other and are entwined by other strands.

A still further object is to provide a method for making net-likestructures formed of a pair of webs having strands and strand junctionsin which the strands of one web are entwined about crossing strands ofthe other web and are also interwoven with strands of such other web.

These and other objects are accomplished in accordance with the presentinvention by a method in which strands are manipulated to provide anet-like structure including strands and having strand junctions at eachof which strands are disposed in crossing relationship with each otherand are entwined by other strands. The strands employed may bepreformed. Alternately, and as hereafter described in detail, thesestrands may be formed continuously and concomitantly with theirmanipulation into a net-like structure.

in accordance with one preferred mode of practicing the method of thepresent invention, a plurality of separate groups of spaced streams ofstrand-forming material are continuously extruded, with the groups beingarranged in pairs and the pairs of groups being spaced from each other agiven distance along a common plane which extends between the groups ofeach pair of groups. Each pair of groups of streams are revolved aboutthe axis which extends between the respective groups of each such pairof groups with at least the stream in each such group which is nearestto its axis of revolution, but less than all of the streams of each suchgroup, being moved through an angle of 1 while the remainder of thestreams of each such group are moved through an angle of 360. The groupsof streams of each pair of groups are then moved relatively in adirection parallel to the common plane to rearrange at least certain ofthe groups of streams into pairs with other groups. The streams are setinto strands concomitantly with the extrusion thereof and bycontinuously repeating the above sequence of movements, simultaneouslywith the extrusion of the groups of streams of strand-forming material,net-like structures having desired patterns of strands and strandjunctions are provided.

As indicated by the term group, at least two streams are included ineach group. The respective groups of sueams of each pair of groups mayinclude a like or difi'erent number of streams. The maximum number ofstrands in each group of streams will be controlled only by limitationsimposed by the apparatus employed in the practice of the method and theability to maintain the streams of each group in spaced relationshipduring the extrusion and setting thereof. The spacing between streams inthe respective groups and the spacing of such streams from the axisextending between the groups of streams of each respective pair ofgroups may differ without adversely afiecting the results obtained inthe practice of the method of the present invention.

Relative movement of the groups of each pair of groups may be effected,for example, by moving the groups of streams along one side of thecommon plane while the groups of streams along the opposite side of thecommon plane are held stationary. Alternatively, the groups of streamsalong opposite sides of the common plane may be moved in the samedirection, but at difierent rates of speed, or in opposite directionsrelative to such common plane. When moved, the groups of streams alongthe respective sides of the common plane are moved in unison and at thesame rate of speed. The rate at which relative movement of the groups ofstreams is effected may be changed periodically or randomly during themethod to vary the pattern of strands in the finished net-likestructure.

Preferably, all of the streams in the pairs of groups are moved inunison, at constant rates of speed, and in the same direction when suchpairs of groups are revolved. That is, during any particular revolutionof the respective pairs of groups, the streams thereof will all move ineither a clockwise or counterclockwise direction about an axis betweenthe groups of streams of each such pair of groups. Desirably, thestreams of each paired group of streams which are revolved through anangle of only l80 and the streams of such groups which are revolvedthrough an angle of 360 commence and temiinate their turning movementstogether.

The above-described preferred method may be varied, for example, byhaving the streams of the respective paired groups which are beingrevolved through an angle of only 180 move at a different rate of speedthan those streams of such groups which are being revolved through anangle of 360". Although the streams of the respective groups which areto be revolved through a like angle must be moved in unison, the rate atwhich such streams are moved may be varied during the revolutionthereof. Further, the streams of the respective groups which have beendescribed as being revolved through an angle of 360 may be furtherturned through an angle of 180 or multiple thereof so that the strandsformed from such streams are not merely interlaced with other strandsbut are twisted about such other strands in the finished net-likestructure.

Essential for the satisfactory practice of the method of the presentinvention is that the direction of revolution of the pairs of groups ofstreams and the direction of relative movement of the groups in thepairs of groups be reversed after the respective alternate movement hasbeen completed. Stated differently, the groups along one or both sidesof the common plane which are moved parallel to the common plane arereversed in direction after each revolution of pairs of groups ofstreams, and the direction of revolution of pairs of groups of streamsare also reversed after each movement of groups of streams parallel tothe common plane. For example, in the instance where pairs of groups ofstreams have been revolved in a clockwise direction and the groups alongonly one side of the common plane have been moved to the left to providefor relative movement between the groups of the pairs of groups ofstreams, the rearranged pairs of groups of streams would now be revolvedin a counterclockwise direction and would be followed by the groupsalong the one side of the common plane being moved to the right.

By following the above procedure, the resulting netlike structureincludes strands which are crossed or interlaced with each other into aweb having a plain weave pattern, and strands which define a second webin which the strands are interlinked with each other and are bothinterlaced with strands of the woven web and entwined about the same intheir areas of crossing. If the streams from which the strands in thenet-like structure is formed are only partially set and still tackybefore contact therebetween or set only after they have contacted, theinterlaced and interlinked strands will be bonded together at theirlocations of crossing so that strong, integral junctions will beprovided. On the other hand, if the streams forming the strands of thenet-like structure are set, at least on the surfaces thereof, prior toany contact therebetween, each strand remains independent of the othersat their locations of crossing. In both instances, however, theinterlinked strands will serve to at least partially stabilize and, ineffect, lock strands of the woven web against movement in certaindirections.

More particularly, when revolving the pairs of groups of strearm, thestreams of the respective groups which are moved through an angle ofonly alternately with the movement thereof in directions parallel to thecommon plane, maintain the same direction of travel parallel to thecommon plane. In other words, a stream of a paired group of streamswhich was moved parallel to the common plane in a leftward directionwill continue to be moved in the same leftward direction after the groupwhich includes such stream has been revolved through an angle of only180. On the other hand, the streams of the respective groups of streamswhich are revolved through an angle of 360 are returned to theiroriginal positions and will either remain stationary or will be moved ina direction opposite to their prior movement when relative movementsbetween the groups is effected. Thus, if groups each containing fourstreams are paired and two of each group are revolved through an angleof only 180 while the remaining two of each group are turned through360", two of the strands formed from streams in such groups will merelycross two other streams. The remaining four strands will be entwinedabout the crossing strands, with two extending in a clockwise directionand two in a counterclockwise direction.

The apparatus employed in the method of the present invention includes aplurality of nozzles, each being of semi-circular configuration andincluding a semi-cylindrical section and a mating semi-circular section.The nozzles are arranged in spaced relationship along each of theopposite sides of a common plane, with their flat sides disposed alongthe common plane and with the nozzles along one side of the common planebeing paired with like nozzles along the opposite side of the commonplane. Each of the nozzle sections includes at least one extrusionorifice to which flowable strand-forming material is delivered and fromwhich such strand-forming material is extruded as a continuous streamand set into a strand.

Means are provided for relatively shifting the nozzles of the respectivepairs of nozzles in directions parallel to the common plane to rearrangeat least some of the nozzles along one side of the common plane intopairs with like nozzles along the other side of such plane. Operativealternately with the shifting means are means for revolving thesemi-circular and the semi-cylindrical sections of the respective pairsof nozzles concomitantly about an axis extending centrally between suchnozzles.

Relative movement between the nozzles of the respective pairs of nozzlesmay be effected, for example, by holding the nozzles along one side ofthe common plane stationary while the nozzles along the other side ofsuch plane are reciprocated. Preferably, the nozzles along both sides ofthe common plane are reciprocated in 180 out-of-phase relationship, withthe means for revolving the semi-circular and semi-cylindrical sectionsof the respective pairs of noules being operative alternately with eachstroke of the nozzle reciprocating means. The nozzle revolving meansincludes means for moving the semi-circular sections of the respectivepairs of nozzles through an angle of only 180 and means for moving thesemi-cylindrical sections of such respective pairs of nozzles through anangle of 360 alternately with the operation of the shiftmg means.

As with conventional apparatus for making net-like structures, suitablemeans are provided for drawing the finished net-like structure away fromthe extrusion means itself.

The net-like structures made by the method of the present invention maybe formed of any continuous preformed strands which possess thenecessary flexibility for manipulation into an entwined relationship.When the net-like structure is made of strands which are formedcontinuously and concomitantly with their manipulation, a variety offiber-forming materials may be employed, which are referred to by theterms plastic" and strand-forming materials," including polyoleflns,such as polyethylene, polypropylene, polybutylene, polystyrene,polystyrene-acrylonitrile blends, acrylonitrile butadiene-styreneblends, acrylonitrile-butadiene copolymers, polybutene, polyisobutylene,polyisoprene, and isobutyleneisoprene copolymers; halogenated olefins,such as polyfluoroethylene, polychlorofluoroethylene,polychlorofluoropropylene, polyvinyl chloride, polyvinylidene chloride,polyvinyl chloride-acetate copolymer, polyvinyl chloridepolypropylenecopolymer, polychloroprene, fluoroinated ethylenepropylene copolymers,vinylidene fluoridechlorotrifluoroethylene copolymers, and vinylidenefluoride-hexafluoropropylene copolymers; polyesters, such aspolyethylene terephthalate and copolymers thereof and polycarbonate;polyamides, such as polyhexamethyl adipamide, polycaprolactam,polyhexamethylene sebacarnide, poly -aminoundecanoic acid; polyvinylacetates; chlorinated polyethers, such as, ethylacrylate-chloroethylenevinyl ether copolymer; acrylic resins, such as polyacrylonitrile,polyacrylates and methacrylates; natural rubbers; compounded silicones,polyurethanes; polyethers, such as polyforrnaldehyde,formaldehyde-ethylene oxide copolymers, and polytrioxane; polysulfurresins, such as polysulfones and polysulfides; water-soluble, alkalisoluble, and organic solvent-soluble cellulose esters and ethers, suchas cellulose nitrate, cellulose acetate, cellulose butyrate, cellulosepropionate, ethyl cellulose, viscose or cellulose xanthate,cuproamrnonium cellulose, and carboxymethyl cellulose; glasses; metals,etc. Such materials may include various additives such as stabilizers,dyes, foaming agents, etc., if so desired.

For a greater understanding of this invention, reference is made to thefollowing detailed description and drawing in which FIG. 1 is a frontview of the apparatus employed in the practice of the method of thepresent invention, with a portion of such apparatus being shown insection;

FIG. 2 is a horizontal section taken substantially along the lines llllof FIG. 1;

FIG. 3 is a partial vertical section taken transversely through theapparatus substantially along the line Ill- III of FIG. 2; and

FIG. 4 is a diagrammatic illustration of a portion of one form ofnet-like structure made by the method of the present invention.

With reference to the drawing, the apparatus employed in the method ofthe present invention includes a pair of vertical support members 15 and17 and a pair of channels 19 which are fixed to the upper portions ofthe support members 15 and 17 in laterally spaced and opposingrelationship with each other. Each of the channels 19 includes a web 20,a pair of flanges 21 and 23, and a wall 25 projecting from the channelweb 20 and cooperating with the adjacent flange 21 to define a slot 27.Plates 29 and 31, extending through openings 33 and 35 in the supportmembers 15 and 17, are mounted for sliding movement along the slots 27,with their opposing edges 37 and 39, respectively, in abuttingrelationship.

Plates 41 and 43 are also mounted for sliding movement relative to thechannels 19 and are formed with edge portions 45 of reduced thicknesswhich are received within correspondingly spaced slots 47 formed in thechannel flanges 23. The plates 41 and 43 are also disposed with theiropposing longitudinal edges in abutting relationship and appropriatelyshaped openings 49 and 51 are formed in the support members 15 and 17,respectively, to accommodate such plates.

The support members 15 and 17, channels 19, and the pairs of plates 29and 31 and 41 and 43 together define a closed chamber 53. A flowablestrand-fomiing material is delivered under pressure into the chamber 53through a conduit 55 from a suitable source, not shown. Gaskets areprovided along the edges of the openings 33, 35 and 49 and 51 in thesupport members 15 and 17 to prevent leakage of strand-forming materialduring sliding movement of the plates 29, 31, 41 and 43 relative to suchsupport members. A tank 57 is provided for containing a suitable settingliquid 59 in the area below the plates 29 and 31.

The abutting edges 37 and 39 of the plates 29 and 31 and the abuttingedges of the plates 41 and 43 all lie in a common vertical plane. Aseries of like, equally spaced semi-circular recesses 61 and 63 areformed along the edges 37 and 39 of the plates 29 and 31, respectively.A nozzle 65 is positioned within each of the plate recesses 61 and 63and includes a semi-cylindrical section 67 and a mating semi-circularsection 69.

The nozzle sections 67 are each formed with an outer arcuate wall 71,which conforms with the plate recesses 61 and 63, an inner arcuate wall73, flat surfaces 75, and a flange 77 at its uppermost end whichprojects over and rests upon the top surface of the respective plates 29and 31. The nozzle sections 69 are each formed with an arcuate wall 79,which conforms with the arcuate wall 73 in the nozzle sections 67, aflat wall 81 and a flange 83, the latter of which extends into a recess85 formed in the top surface of the respective nozzle sections 67.

The plates 41 and 43 are also provided with a series of like recesses 87and 89 along the respective abutting edges, with the spacing between therecesses in such series being substantially equal to that of therecesses 61 and 63 in the plates 29 and 31. Like semi-circular members91, which may be of solid or closed construction, are positioned withinthe respective recesses 87 and 89. Each such member 91 includes anarcuate wall 93, which conforms to the recesses 87 and 89, and a flatwall 95. The semi-circular sections 69 of the nozzles 65 and the members91 are intended to move in unison with each other and thus each suchnozzle section 69 is rigidly connected to an individual member 91 by astrut 97.

Means are provided for longitudinally moving or shifting correspondingplates in the pairs of plates 29 and 31 and 41 and 43 in unison atselected time intervals, as hereafter described. Of course, during suchmovement the flat surfaces of the respective nozzle sections and theflat surfaces of the members 91 are disposed in the common plane, asdefined by the abutting surfaces of the pair of plates 29 and 31 and thepair of plates 41 and 43. Preferably, both of the plates of each suchpair of plates are shifted longitudinally in opposite directionsrelative to each other, with corresponding plates in such two pairs ofplates moving in unison.

The relative longitudinal movement between the plates 29 and 31 iseffected through pins 99 and 101 which project from the respectiveplates 29 and 31 and ride along grooves 103 and 105 formed in opposingfaces of cams 107 and 109. These cams 107 and 109 are of likeconstruction and are fixed, in [80 out-ofphase relationship, to a shaft111 which is supported by bearings, such as shown at 113, and isintermittently driven by suitable means, not shown. In the particularapparatus illustrated in the drawings, and as more fully describedhereafter, the plates 29 and 31 are moved in opposite directions adistance substantially equal to one-half of the center-to-center spacingof the respec tive recesses 61 and 63 to thereby rearrange the nozzles65 which are carried by such plates into different pairs.

Movement of the plates 29 and 31 is transmitted to the plates 41 and 43through the struts 97 and members 91 so that corresponding plates inthese two pairs of plates will move in unison with each other.Ifdesired, a separate means may be provided for shifling the plates 41and 43 in synchronism with the plates 29 and 31, respectively.

Altemately with the longitudinal sliding movement of the pair of plates29 and 31 and the pair of plates 41 and 43, the respective nozzlesections 67 and 69 of aligned or paired nozzles 65 are independentlyrevolved, with the nozzle sections 67 being turned through an arc of360, or further multiples of l80, while the nozzle sections 69 arecarried through an arc of only l80. This revolving movement of thenozzle sections 67 is efl'ected by gear racks 1 and 117 which are drivenby segment gears 121 and 123 and are in meshing engagement with gearteeth 119 formed along the outer walls 71 of such sections. The channelflanges 21 are rabbeted at 125 and, with the plates 29 and 31, defineguide slots for the racks 115 and 117. For reasons as hereafterdescribed, gear teeth are omitted from along selected lengths of theopposing sides of the racks 115 and 117, as indicated at 127 and 129.

Revolving movement is likewise imparted to the nozzle sections 69 byracks 131 and 133 which mesh with semi-circular gears 135 and 137 fixedto the upper ends of the members 91. Suitable, means, not shown, areprovided for maintaining the racks 131 and 133 in meshing engagementwith the gears 135 and 137. The racks 131 and 133 are each driven by aseparate segment gear 139, with both such gears being driven insynchronized relationship to shift the racks 131 and 133 in oppositedirections relative to each other. As with the racks and 117, teeth areomitted from selected lengths of each of the racks 131 and 133 forreasons as hereafter described.

For the sake of simplicity, the nozzle sections 67 and 69 are eachillustrated as having a single extrusion orifice 141 and 143,respectively. It will be understood that the number of such orificesextending through the respective nozzle sections may be varied withoutdeparting from the teachings of the present invention.

With the various elements of the apparatus in stationary startingpositions as shown in FIGS. 1, 2 and 3, a flowable strand-formingmaterial, such as molten thermoplastic material, is delivered underpressure into the chamber 53 through the conduit 55. Such flowablestrand-forming material is continuously extruded from all orifices 141and 143 in the nozzle sections 67 and 69 as streams which are set intostrands in the liquid 59, which may be cool water.

The cams 107 and 109 are now operated to shift the plates 29 and 31 inopposite directions a distance equal to one-half of the center-to-centerspacing of the respective plate recesses 61 and 63 to thus align nozzles65 in the plate 29 with different nozzles 65 in the plate 31. Forexample, the plate 29 may be moved to the left, as viewed in FIG. 2,while the plate 31 is simultaneously moved to the right to therebyrearrange the nozzles 65 along opposite sides of the common plane, asdefined by the plate edges 37 and 39, into different pairs. During thismovement, streams of strand-forming material are continuously extrudedfrom the orifices 141 and 143 of all of the nozzle sections 67 and 69,and are merely moved in unison in directions parallel to the commonplane.

The members 91, being rigidly connected to the nozzle sections 69 by thestruts 97, will move in unison with the nozzle sections 69 and will urgethe plates 41 and 43 in the same directions as the plates 29 and 31,respectively. During the above-described stage of the method, the gearracks 115, 117, 131 and 133 are not in meshing engagement with theirdriving segment gears and thus such racks are free to shift with theplates 29, 31, 41 and 43, respectively.

The nozzle sections 67 and 69 of the rearranged pairs of nozzles 65 arenow separately revolved. More particularly, the racks 115 and 117 aredriven by the gears 121 and 123 in opposite directions relative to eachother, as for example to the left and right, respectively, as viewed inFIG. 2. In this manner the nozzle sections 67 of each pair of alignednozzles 65 are revolved in a clockwise direction. The degree to whichthe racks 115 and 117 are shifted must be such as to rotate the sections67 of aligned nozzles 65 through a complete 360 circle.

Concornitantly with the revolving of the nozzle sections 67 of thepaired nozzles 65, the nozzle sections 69 of such aligned nozzles 65 arerevolved by shifting the racks 131 and 133 in opposite directionsrelative to each other by the segment gears 139. The racks 131 and 133are shifted in the same directions as the racks 115 and 1 17,respectively, but only to such degree as to revolve the nozzle sections69 through an arc of only 180.

During the revolving of the sections of aligned nozzles 65, the nozzlesections 67 carried by the plates 29 and 31 which are not paired oraligned with like nozzle sections 67 in the opposing of such plates willlie opposite to the portions 127 and 129 of the racks 115 and 117,respectively. Since such rack portions 127 and 129 are free of gearteeth, no revolving movement will be imparted to the noule sections 67which are adjacent thereto when such racks are shifted. Likewise, themembers 91 which are rigidly connected to nozzle sections 69 of unpairednozzles 65 will be disposed opposite to the portions of the racks 131and 133 from which teeth are omitted. Thus, no turning movement will beimparted to these particular nozfle sections 69 when the racks 131 and133 are shifted.

During the above-described movements of the nozzle sections of alignednozfles 65, the nozzle sections 67, being revolved 360, are returned totheir original positions. The nozzle sections 69, however, are rotatedthrough an angle of only 180 so that the sections 69 of each pair ofaligned nozzles 65 merely exchange positions. That is, with the sections69 of the nozzles 65 which are carried by the plate 29 being transferredto the plate 31, and the sections 69 of nozzles 65 carried by the plates31 being transferred to the plate 29.

The plates 29 and 31 are now reciprocated by the cams 107 and 109 in thesame manner as described above, except in opposite directions to theirprior movement. As viewed in FIG. 2 the plate 29 would now be moved tothe right while the plate 31 is moved to the left, with both such platesmoving simultaneously a distance equal to one-half of thecenter-to-center spacing between the plate recesses 61 and 63. Theplates 41 and 43 will also be shifted longitudinally in oppositedirections relative to each other in a manner as heretofore described,with the plate 41 moving in unison with the plate 29 and the plate 43moving concomitantly with the plate 31.

It will be noted that during this reciprocation of the plates 29 and 31,most of the nozzle sections 69 of the nozzles 65 which were heretoforepaired and transferred from one of the plates 29 and 31 to the otherthereof travel in the same direction relative to the common plane asthey did during the prior reciprocation of such plates. Moreparticularly, during the initial reciprocation of the plates 29 and 31,all nozzle sections 69 carried by the plate 29 were all moved to theleft while all nozzle sections 69 carried by the plate 31 were all movedto the right. During the subsequent reciprocation of these plates, theplate 29 is moved to the right while the plate 31 is moved to the left.The nozzle sections 69 of paired nozzles 65 are revolved through an arcof 180 inbetween such shifts of the plates, however, so that sections 69of such paired nozzles are merely transferred from one plate 29 and 31to the other thereof. Thus, except for the sections 69 of the endmostnozzles 65 in each such series of nozzles, the sections 69 will be movedin the same leftward or rightward direction relative to the common planeduring both of the reciprocating movements of the plates 29 and 31. Thestrands which are formed from the streams of strand-forming materialextruded from the orifices 143 of these particular nozzle sections 69are indicated at 145 and 147, and as shown at junction A in FIG. 4, thestrand 145 overlies the strand 147.

As heretofore mentioned, the sections 69 of the endmost nozzles 65 arenot turned when paired nozzles 65 in the plates 29 and 31 are revolvedand therefore, remain along the same side during both of the describedreciprocating movements of the plates 29 and 31. For example, thesection 69 of the nozzle 65 shown at the extreme left of the plate 29 inFIG. 2 merely travels with the plate 29 when such plate is shifted tothe left and subsequently to the right. This particular nozzle section69 will be transferred to the plate 31 when paired nozzles aresubsequently revolved and will thereafter travel to the right, as viewedin FIG. 2, until it again becomes part of a nozzle which is located atone end of a series of nozzles.

On the other hand, the nozzle sections 67 of the paired nozzles 65 whichare returned to their original plates 29 and 31 during each 360revolution thereof will travel, during the last-mentioned reciprocationof the plates 29 and 31, in a direction opposite to that in which theywere moved during the initial reciprocation of such plates. The strandsformed from the streams of strand-forming material extruded from theorifices 141 of these particular nozzle sections 67 are indicated at 151and 153, and as shown at junction A in FIG. 4, the strands 151 and 153are entwined about the crossing strands 145 and 147 and are alsointerlaced with each other as well as with the strands 145 and 147.

Following the second described reciprocation of the plates 29 and 31relative to each other, the now paired nozzle sections 69 are eachrevolved by the racks I31 and 133 through only a arc, with this movementbeing in a direction opposite to the previous revolution of pairednozzle sections 69; namely, in a counterclockwise direction as viewed inFIG. 2. As a result, the strands formed from the streams extruded fromsuch sections 69 are disposed as shown at junction B in FIG. 4, with astrand lying beneath a crossing strand 147.

Concomitantly with the above-mentioned revolution of the sections 69,the sections 67 of the paired nozzles 65 are turned through a complete360 circle whereby strands 151 and 153 formed from streams extruded fromsuch sections, as shown at junction B, are entwined about the crossingstrands 145 and 147. As at junction A, and junction B the strands 151and 153 are interlaced with each other and with the strands 145 and 147.It will be noted, however, that the strands 151 and 153 each bend inopposite directions at junctions A and B.

Reciprocation of the plates 29 and 31 is then effected by shifting thesame in directions as initially described and is followed by revolvingthe paired nozzle sections 67 and the separate but mating nozzlesections 69 in clockwise directions. By repeating the above-describedsteps, concomitantly with the extrusion and setting of the streams ofstrand-forming material a continuous net-like structure is providedhaving strand and strand junctions as illustrated in FIG.

From the above description, and as shown in FIG. 4, strands 145 and 147extend diagonally of the net-like structure and are interlaced with eachother to provide a web having a plain weave. That is, such diagonalstrands 145 and 147 extend under a crossing strand at one junction andthen over a crossing strand at an adjacent junction. On the other hand,the strands 151 and 153 extend along zig-zag paths and are interlinkedwith each other to provide a second web. It will be further noted thatthe strands 145 and 147 pass over and under strands 151 and 153 of thissecond web at the different junctions and thus the strands of one webare interwoven with strands of the other of such strands. Of particularimportance is that the strands l] and 153, being entwined about thestrands 145 and 147 at their crossing points, do restrict shifting ofthe strands of the woven web relative to each other.

If in the practice of the above-described method the extruded streamsare brought into contact while still in a tacky condition, the resultingstrands will be adhered to each other at the strand junctions.Preferably, however, the streams are at least surface set prior tocontact to provide a more flexible net-like structure. Variations fromthe net-like structure described may be provided, for example, byreciprocating the plates 29 and 31 further multiples of thecenter-to-center spacing between plate recesses 61 and 63 and/or byrevolving the sections 67 of the paired nozzles 65 through arcs of 360plus further multiples of 180. With this latter procedure, the strands151 and 153 formed from streams extruded from the noule sections 67would be twisted one or more turns about the strands 145 and 147 attheir crossing points.

While the net-like structure has been described as being fonnedconcomitantly of the manufacture of strands, net-like structures may beproduced from preformed strands. In this instance, the preformed strandsare merely laced through the nozzle orifices after which such strandsand their supply sources are manipulated in accordance with the methodof the present invention, as described above.

l claim:

1. A method of making net-like structures including the steps ofdelivering a plurality of separate groups of continuous strands with thegroups arranged in pairs and the pairs of groups being spaced from eachother a given distance along a common plane which extends between thegroups of each pair of groups, revolving each pair of groups of strandsabout an axis which extends between the respective groups of each pairof groups with at least the strand of each such group which is nearestto its axis of revolution but less than all of the strands of each suchgroup being moved through an angle of only while the remainder of thestrands in each such group are moved through an angle of 360, relativelymoving the groups of strands in a direction parallel to the common planeto rearrange at least certain of the groups of strands into pairs withother groups of strands and continuously repeating the above sequence ofmovements simultaneously with the continuous delivery of the groups ofstrands.

2. A method as defined in claim 1 wherein all strands in each pair ofgroups of strands are revolved in the same direction relative to theaxis which extends ll /i" lle rli%il s"lfs&%li3 fififil iwlli filmdirection of revolution of each pair of groups is reversed after eachrelative movement of the groups of strands in a direction parallel tothe common plane.

4. A method as defined in claim 3 wherein the relative movement of thegroups of strands is effected by moving at least the groups of strandslocated along one side of the common plane and wherein the direction ofsuch movement is reversed after each revolution of the pairs of groupsof strands.

5. A method as defined in claim 1 wherein the strands are formed byextruding the streams of strandfonning material continuously andconcomitantly with the repeated sequence of movements of the groups ofstrands and wherein the extruded streams are set into strands prior toany contact therebetweenr 6. A method as defined in claim 1 wherein thestrands are formed by extruding streams of strandfonning materialcontinuously and concomitantly with the repeated sequence of movementsof the groups of strands and wherein the extruded streams are set intostrands after such streams have contacted with each other.

I i l i i 5 53 I UNITED STATES PATENT OFFICE I CERTIFICATE OF CORRECTIONPatent No. 3 ,6 .380 Dated Auqggi 22 1972 Inventor(s) Theodore H.Fairbanks in the above-identified patent It is certified that errorappears corrected as shown below:

and that said Letters Patent are hereby Front page, left column, line 5,insert "('73) Assignee: FMC Corporation, Philadelphia, Pa.". Col. 2,line 45,

t such. Col. 8, line 2, after after "each" inser "Suitable" delete thecomma Signed and sealed this 9th day of January 1973.

(SEAL) Attest:

EDWARD MJ LEICHER, JR. ROBERT GOTTSCHALK Commissioner of PatentsAttesting Officer

2. A method as defined in claim 1 wherein all strands in each pair ofgroups of strands are revolved in the same direction relative to theaxis which extends between the respective groups of each pair of groups.3. A method as defined in claim 2 wherein the direction of revolution ofeach pair of groups is reversed after each relative movement of thegroups of strands in a direction parallel to the common plane.
 4. Amethod as defined in claim 3 wherein the relative movement of the groupsof strands is effected by moving at least the groups of strands locatedalong one side of the common plane and wherein the direction of suchmovement is reversed after each revolution of the pairs of groups ofstrands.
 5. A method as defined in claim 1 wherein the strands areformed by extruding the streams of strand-forming material continuouslyand concomitantly with the repeated sequence of movements of the groupsof strands and wherein the extruded streams are set into strands priorto any contact therebetween.
 6. A method as defined in claim 1 whereinthe strands are formed by extruding streams of strand-forming materialcontinuously and concomitantly with the repeated sequence of movementsof the groups of strands and wherein the extruded streams are set intostrands after such streams have contacted with each other.